I was hoping to grab the wallpaper png from carlz28's zip file. I can add jpegs as wallpaper, but unfortunately I have no idea what to do with the png file to make it the wallpaper.
Just copy the png to your SD card. Then long-press and bring up the wallpaper menus. Select gallery. Once in there, navigate to where you put it on your SD card) You may have to reboot before trying to install the wallpaper however. Sometimes gallery doesn't update 'live'...not sure why it does this. I've run into this problem a few times. Reboot fixes it. Allows the reading of SD card (and to create thumbnails of newly added pictures)
There is no issue with using pngs as a wallpaper. Actually, its probably better as there is no banding/pixelating issues with pngs.
As for anybody else's problems....remember, this is a theme. Many changes to icons have been made, but also some changes to the framework-res.apk as well.
When testing this theme, I did so over a completely stock ROM/theme (FRF57). You may or may not have changes done to other files that need to stay the way they are in order for certain features.
My files installed properly over Bugless Beastv.4 and Jrummy's newest ROM (haven't tried it on ChevyNo1's ROM though).
So it should work for you as well.
With that said, installing on top of another 'already installed theme' is not recommended.
To those having issues downloading the themes, a few suggestions:
At all possibilities, please download over wifi or onto your computer first (then transfer to SD card).
Make sure your download doesn't get interrupted..i.e a text message or phone call, etc.
This seems to be an issue for lots of people (interruptions).
Again, I have to restate that this was tested on stock themes/ROMs first.
I haven't tried on top of other themes (as that's not the best practice anyway).
Just to note, I downloaded both my theme and roberj13's theme from the links provided and they both installed fine for me.
Maybe it's an issue with downloading from DroidForums.net that some are having.
If so, you can try from my own server linked below.
Mods, feel free to add this link to the OP
http://www.carlz28.com/carlz28_J4_theme_files.zip
Any other questions, feel free to ask